PROCEDURE: tplot_panel [,time,y] INPUTS: (optional) time: dblarr of time values associated with a variable to overplot in a designated "tplot" panel. y: array of variable values to be plotted. KEYWORDS: VARIABLE: (string) name of previously plotted tplot variable. OPLOTVAR: Data that will be plotted on top of the selected panel DELTATIME: Named variable in which time offset is returned. PANEL: Returns panel number of designated tplot variable. PSYM: Sets the IDL plot PSYM value for overplot data. PURPOSE: Sets the graphics parameters to the specified tplot panel. The time offset is returned through the optional keyword DELTATIME. LAST MODIFICATION: @(#)tplot_panel.pro 1.9 02/04/17